Spiral groove bearings and rotating anode X-ray tubes designed for rotation frequencies higher than 150 Hz may face lubricant leakage problems at the sealing surfaces of the bearing parts. High centrifugal forces acting on the lubricant and strong mechanical forces acting on the bearing parts may influence the effective tightness against lubricant along the entrance gaps of the sealing. In particular, in the case of spiral groove bearings, the contact surfaces of the rotating bearing parts may have to fulfil the functionality of sealing against lubricant loss and exact positioning of the axial bearing surfaces.
U.S. Pat. No. 5,077,775 discloses a rotary-anode X-ray tube comprising at least two spiral groove bearings.